They cannot arbitrarily make wild gambles because they feel like it - they have to operate within established risk parameters that are approved by several regulatory bodies and internal controls.

Fast forward three years: He’s moved out, and the property now nets him close to $1,200 a month in profit after expenses.

That's not a "net profit" of $550/month because you haven't accounted for vacancy, maintenance, capex, or other expenses.

Am I being dumb by NOT waiting, because it’s unlikely - I assume - my next deal will be as profitable (I got very lucky on this one!)

I worked them, remodeled them and made very little money and eventually sold them for little to no profit.

At the acquisition price points, and the market value of the units if you do decide to go wit a pm you’ll find yourself not being very profitable as most pm’s will charge $75 per unit min or 8-10% of gross rental income.

You can make great profits flipping houses, but you can also lose a ton if you don't do it right.That said, I encourage you to be in touch with an investor friendly agent in Indy.

However as you correctly point out this is far more risky and or its risk capital compared to buying a income property.. but the reward can be strati-spherically higher .. not just a little bit but it can be life changing profits on some of these deals.

I found a killer deal, put 1k down as EMD and then wholesaled it for a nice profit. 

Give them a portion of the profits from the STRs and have a buy-out clause when you have the funds to refinance.I am sure there are many other potential options for you to look into, but just off the top of my head these 5 came to mind.